Medical diagnostic imaging with real-time scan conversion

ABSTRACT

Display or pixel values are scan converted from ultrasound data on the fly. As each pixel is to receive display values, the display value is determined. Scan conversion is performed sequentially, with each new value being determined in synchronization with reading display values out to the display. Rather than storage in a raster buffer, scan converted display values are output to the display while other display values for a same image are being converted.

BACKGROUND

The present invention relates to medical imaging. In particular, asystem and method of scan conversion is provided.

In medical diagnostic ultrasound imaging, a patient is scanned in alinear, sector, or Vector® format. In response to the scan, ultrasounddata is acquired in a polar coordinate format. The ultrasound data isused to generate an image on a display. The display format has aCartesian coordinate format. The ultrasound data is converted from polaror Cartesian acoustic coordinate to the Cartesian display coordinateformat. The ultrasound data is also converted from intensity or estimateinformation into red, green, blue or other video signal for display.

The display values resulting from scan conversion are output to a rasterbuffer. Display values for an entire image are stored in the bufferbefore reading out to the display. Graphics information, such as textand borders, are added to the data in the buffer. The graphicsinformation or overlay is provided from a different video source.

Storage in the buffer introduces a time delay between scanning anddisplay. The time delay may be reduced by providing two buffers. Displayvalues for one image are read into one buffer while display values for adifferent image are read out of the other buffer. The buffers are usedin a ping-pong fashion between reading in and reading out displayvalues. However, there is still latency introduced by reading in or outall the display values for an image. The single or double buffer alsouses space, increases cost, and increases power usage.

BRIEF SUMMARY

By way of introduction, the preferred embodiments described belowinclude systems, methods, computer readable media, and instructions forscan converting in medical imaging. Display or pixel values are scanconverted from ultrasound data on the fly. As each pixel is to receivedisplay values, the display value is determined. Scan conversion isperformed sequentially, with each new value being determined insynchronization with reading display values out to the display. Ratherthan storage of an entire image in a raster buffer, scan converteddisplay values are output to the display while other display values fora same image are being converted.

According to a first aspect, a method of scan conversion is provided inmedical diagnostic ultrasound imaging. Pixel values are sequentiallyoutput to a display. The pixel values are scan converted for the output.Each pixel value is scan converted and output prior to completing scanconverting of a subsequent pixel value for a same image.

In a second aspect, a system is provided for scan conversion in medicaldiagnostic ultrasound imaging. A processor is operable to convertultrasound data in an acoustic coordinate format to display values in aCartesian coordinate format. A display is operable to receive thedisplay values and to display an image with the display values. Theimage is displayed without a raster buffer from conversion by theprocessor to display of the image by the display.

In a third aspect, a computer-readable medium has stored thereininstructions executable by a processor for scan converting in ultrasoundimaging. The instructions include generating a display image with videodisplay color values, and calculating the video display color valuesfrom acoustic data. The calculating is at a rate synchronized withoutput of the video display color values to the display image where eachof the video display color values is calculated as the video displaycolor value is output to a pixel of the display image.

The present invention is defined by the following claims, and nothing inthis section should be taken as a limitation on those claims. Furtheraspects and advantages of the invention are discussed below inconjunction with the preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The components and the figures are not necessarily to scale, emphasisinstead being placed upon illustrating the principles of the invention.Moreover, in the figures, like reference numerals designatecorresponding parts throughout the different views.

FIG. 1 is a block diagram of one embodiment of an imaging system forscan conversion;

FIG. 2 is an example of a circuit or logic for scan conversion andcalculating display values;

FIG. 3 is a timing diagram of one embodiment of scan converting andoutputting display values to a display;

FIG. 4 is a flowchart of one embodiment of a method for scan converting;and

FIG. 5 is an example of a circuit or logic for scan conversion.

DETAILED DESCRIPTION OF THE DRAWINGS AND PRESENTLY PREFERRED EMBODIMENTS

A display image is generated for a medical ultrasound machine. Videodisplay color values are calculated in real time at the rate required bythe display. The values are calculated for each of the image components,such as for B-mode, C-mode (i.e., color, flow, or Doppler), and overlayuser interface graphics. Video signals may be generated withoutconversion of a complete raster image for storage and combination withoverlay graphics. The video display color value for a pixel iscalculated from the possible image components in real time at the rateat which data is provided to the display.

FIG. 1 shows one embodiment of a medical diagnostic ultrasound imagingsystem 100. Any known or future dedicated ultrasound imaging system maybe used. In other embodiments, the imaging system 100 may be a computer,a workstation, a server, and/or an image database system.

In one embodiment, the imaging system 100 is a cart based imagingsystem. In another embodiment, the imaging system 100 is a portablesystem, such as a briefcase-sized system or laptop computer basedsystem. Other embodiments include handheld ultrasound systems. Forexample, one or more housings are provided where the entire system issmall and light enough to be carried in one or both hands and/or worn bya user. The processors, transducer, display, and/or other components areprovided in a single housing. In another example, a transducer is in onehousing to be held by a person, and the imaging components and displayare in another housing to be held by a person. Coaxial cables connectthe two housings. As another example, the transducer and imagingcomponents are in one housing and the display is in another housinghinged with the first housing. In any embodiment, the entire handheldsystem may weigh less than about 6 pounds, but may weigh more. Forexample, the handheld system weighs less 4than about 2 pounds, a weightaround more commonly used medical equipment and more naturally born bymedical professionals without burden. About allows for manufacturingtolerances.

The imaging system 100 performs scan conversion from an acquisition scanformat to a display format. Coordinate conversion is provided.Conversion from ultrasound values to display values, such as red, green,blue values, is provided.

The imaging system 100 includes, but is not limited to, a transducer102, an analog-to-digital converter (“ADC”) 106, a receive beamformer110, a processor 112, a display 116, an input device 126, a processor120, and a memory 122. Additional, different, or fewer components may beprovided. For example, probe electronics and a transmit beamformer areprovided. In addition, the processor 112 and the processor 120 may becombined into one processor. The processor 112 may be separated intodifferent components, such as one or more detectors and a scanconverter. The ADC 106 may be a part of the receive beamformer 110. Theinput device 126 and/or the display 116 may be separate from butoperable to communicate with the imaging system 100. Any or all of theelectronics may be integrated in a single housing or few housings.

The imaging system 100, including the processor 112, is free of a rasterbuffer. Images are displayed without a raster buffer. For example, araster buffer for storing display values for an entire image is notprovided from scan conversion by the processor 112 to display of theimage by the display. The entire image is the scan portion, but may alsoinclude background regions of the display screen. The image is displayedwithout storing display values for all pixels of the image. A buffer maybe provided for a single display value, such as buffering 8, 16, orother bits for color components, such as for red, green, blue values fora pixel. Larger buffers may be used for 4storing values for a pluralityof pixels, but fewer than for an entire image. For example, a shiftregister may be provided to shift a backlog of display values to pixelsof the display. In other embodiments, a raster buffer for sufficientvalues for an entire image or more is provided.

The processor 120 connects with the memory 122, the display 116, theinput device 126, the transducer 102, the ADC 106, the receivebeamformer 110, and the processor 112. The processor 120 may connectwith more or fewer components. The processor 120 is a main or controlprocessor, such as a microprocessor, or a plurality of processorsoperable to control electronics of the imaging system 100.

The memory 122 is any known or future storage device. The memory 122 isa non-volatile and/or volatile memory, such as a Random Access Memory“RAM” (electronic), a Read-Only Memory “ROM” (electronic), or anErasable Programmable Read-Only Memory (EPROM or Flash memory).

The input device 126 includes a button, a keyboard, a rocker, ajoystick, a trackball, a voice recognition circuit, a mouse, and/or anyother input device for sending commands in response to user activation.In one embodiment, the input device includes a trackball surrounding bybuttons and a keyboard below the trackball and buttons.

The transducer 102 is a single transducer element, transducer array, ora plurality of transducer arrays. For example, the transducer 102 is aone dimensional linear phased or curved transducer array. In anotherexample, the transducer is a multi-dimensional transducer array.

The transducer 102 includes one or more elements, such as 64 or 128elements. Each element is a piezoelectric or microelectromechanical(e.g., capacitive membrane ultrasound transducer) transducer device, butother materials or structures may be used to convert between acousticaland electrical energies. For example, the transducer material is amulti-layered transducer material having at least two layers ofpiezoelectric ceramic transducer material. Alternatively, the transducermaterial is a semiconductor substrate with one or more flexiblemembranes (e.g., tens or hundreds for each element) formed within or onthe semiconductor substrate. The transducer elements may also includeany number of different layers, such as matching layers, flex circuitlayers, signal traces, electrodes, a lens and/or a backing block.

The transducer 102, for example, is in an ultrasound probe connectedwith an ultrasound system or is in a housing for the entire system. Thetransducer 102 connects with the components of the system, such asconnecting with the ADC 106, receive beamformer 110, and processor 112.The connections may be within a same housing or through one or morecommunication paths between housings (e.g., cables or wirelessly).

The transducer 102 is operable to receive acoustic signals and convertthe acoustic signals into electrical energy. For example, the transducer102 is operable to acquire ultrasound signals by receiving echo signals.The ultrasound signals include information for C-mode (e.g., Dopplermode, flow mode, velocity, energy, or variance), B-mode (grey-scale),and other tissue or flow information.

The ADC 106 receives signals from the transducer 102. The ADC 106 is asingle or a plurality of any known or future analog-to-digitalconverters operable to sample analog signals, such as echo signals fromtissue. For example, ADCs 106 connect with respective elements(channels) of the transducer 102. The elements connect directly to theADCs 106. Alternatively, multiplexers provide for aperture control toconnect elements to different channels at different times. To reduce anumber of cables, the number of connections from the elements to theADCs 106 may be reduced. Time multiplexing, frequency multiplexing,sub-array mixing, partial beamforming, or other processes for combiningsignals may be used. For example, signals from groups of four or othernumbers of elements are combined onto common data paths by sub-arraymixing, such as disclosed in U.S. Pat. No. 5,573,001 or U.S. PublishedApplication No. 20040002652, the disclosures of which are incorporatedherein by reference.

The receive beamformer 110 receives digital information for the elementsor groups of elements from the ADC 106. Alternatively, the ADC 106 isincorporated into the receive beamformer 110. The receive beamformer 110is an application specific integrated circuit (“ASIC”), processor, fieldprogrammable gate array (“FPGA”), analog components, digital components,integrated components, discrete devices, or combinations thereof. Thereceive beamformer 1 10 includes, but is not limited to, amplifiers,delay memories, a delay calculator, and channel adders for formingbeams.

The receive beamformer 110 apodizes and relatively focuses the receivedsamples. Electrical signals received from the transducer elements arerelatively delayed and summed. Amplifiers may be provided forapodization. In one embodiment, the delays are implemented as memoriesfor storing channel data (e.g., samples from each element). One or morememories may be used. For example, two memories or sets of memoriesoperate in a ping-pong fashion to store data from elements and read dataout for beamforming. Each memory or set stores element data for anentire scan. As one memory or set is storing, the other memory isoutputting. By reading data out of the memory from selected memorylocations, data associated with different amounts of delay is provided.The same data may be used for sequentially forming receive beams alongdifferent scan lines. Other memories may be used, such as a plurality offirst-in, first-out buffers for delaying based on length and/or timingof input into the buffers.

The processor 112 receives beamformed ultrasound data from the receivebeamformer 110. The processor 112 is a digital signal processor,graphics processing unit, main processor, microprocessor, fieldprogrammable gate array, application specific integrated circuit, videoprocessor, graphics processor, analog circuit, digital circuit, orcombinations thereof. The processor 112 is a single device or aplurality of processors. For example, the processor 112 is one centralprocessing unit (“CPU”). Alternatively, the processor 112 is a pluralityof devices in which each device is responsible for sampling and/orprocessing a portion of the data acquired by the imaging system 100.

In one embodiment, the processor 112 includes one or more detectorsand/or filters. For example, a B-mode detector and a Doppler detectordetermine B-mode and C-mode ultrasound data. The B-mode ultrasound datarepresents the intensity of the received echo signals. The C-modeultrasound data represents the motion or flow, such as velocity, power,and/or variance of fluid or tissue motion. For C-mode operation, aclutter filter may be provided to isolate information between tissuesand fluid for C-mode estimation. 4

The processor 112 alternatively or additionally includes a scanconverter. The same hardware operating under different code mayimplement the different operations of the processor 112. For example,coordinate and value conversions are implemented as hardware based statemachines. Alternatively, different hardware of the processor 112implements the different operations.

Scan conversion converts from a scan format to a display format, such asfrom a polar coordinate format of a sector or Vector® scan to aCartesian coordinate format. A linear scan may be provided. Typically,the scan line density (azimuth) and/or sample density (range) is notequal to the display line density, so the acoustic data is converted fora linear scan. Other format conversions than polar to Cartesian may beused.

FIG. 5 represents a circuit, logic, or flow for scan conversion in oneembodiment, but other embodiments without a pyramidal collection of datamay be used. A display pixel location is converted to an acoustic scanlocation, or vise versa. For example, counters output X and Y pixellocation values in order (line-by-line), as represented at 502. Thecount is changed sequentially for pipelined scan conversion. Forconversion, a nearest acoustic location to a display pixel location isidentified at 504. By selecting the ultrasound data at the identifiedacoustic data, the format is converted. As another example, fourrelative weights and corresponding acoustic locations surrounding adisplay pixel location are calculated and identified, respectively. Therelative weights are a function of the relative distance of theidentified acoustic locations to the display pixel location. Theultrasound data at the identified acoustic locations are weighted by thecorresponding weight, combined, and normalized (interpolated) to convertthe format. Other conversions may be used with or without interpolation.The scan conversion provides ultrasound data values for display pixellocations in the Cartesian coordinate or other display coordinateformat.

The spatial extent of B-mode and C-mode data is determined for clippingat 506. The field of view of the B and C-mode data and any region ofinterest border are identified.

The scan conversion is provided for each type of ultrasound data. Forexample, B-mode ultrasound data is scan converted, and C-mode ultrasounddata is scan converted. B-mode, C-mode, and any overlay data areprovided from the buffers 510, 512, and 514, respectively. The sameweights or interpolation may be applied to the different data to reducecalculations. Where the different types of ultrasound data are fromdifferent scan lines or scan distributions, entirely separate scanconversion may be used.

In one embodiment, the scan conversion is performed withoutpre-calculated look-up tables of weights or other interpolationinformation. The processor 112 interpolates based on the user selectedscale, scan format (e.g., number of beams, spatial location of beams,depth, bounding box, and/or clipping), and/or image orientation relativeto the desired screen space to be used for the image. Alternatively, oneor more look-up tables are provided to assist or perform the scanconversion. The collection of data in the pipeline is read and selecteddata is output at 508.

The processor 112 is operable to assign display values as a function ofthe coordinate converted ultrasound data. For example, the processor 112maps the ultrasound scalar values to color display values (red, green,blue (RGB); YUV; or other color format) using a look-up table 516. Theweighting of the ultrasound data for coordinate conversion is performedfor looking up the display color. The B-mode and C-mode data may useseparate look-up tables 518, 520. Grey scale may be implemented bymapping the color components to equal or substantially similar levels(e.g., R=G=B). A function, look-up table, or other device or process maybe used for mapping display values (e.g., RGB or YUV) from inputultrasound data (e.g., intensity and flow data).

The processor 112 is also operable to receive or generate a graphicoverlay, such as data indicating border, text, region of interest, userinterface, or other information to be displayed over or adjacent to theultrasound data from the scan. In one embodiment, the processor 112receives graphic overlay data from a video output of the processor 120,such as by direct memory access from a graphics buffer of the processor120. The processor 120 determines the entire graphic overlay for eachimage and outputs or allows access to the graphic data.

FIG. 2 is an example of a circuit within or process performed by theprocessor 112 for generating display values from input data, such ascoordinate converted ultrasound data and graphic overlay data. Forexample, the processor 112 includes, but is not limited to, a comparator300, a multiplexer 310 (the color select 522 of FIG. 5), a grey-scalelook-up-table (“LUT”) 314, and a color LUT 316. Additional, different,or fewer operations or devices may be provided. In one embodiment, thespecific devices shown are used in the processor 112. Alternatively, theprocessor 112 hardware is programmed with code to perform the operationsrepresented by the blocks shown in FIG. 2.

The multiplexer 310 receives display values for the different types ofdata. The graphics overlay data is received from the processor in adisplay value format (e.g., RGB), but a look-up table or conversionprocess may be provided by the processor 112 in other embodiments.

The B-mode data is input to the look-up table 314. Using any desiredmapping function, each B-mode ultrasound data value is converted to adisplay value, such as RGB components. True grey scale mapping may beused, such as all RGB components being equal. Tinting or intentionaldeviation from true grey scale may be provided to increase dynamicrange.

The C-mode data is input to the look-up table 316. The color or C-modelook-up table 316 is separate from the grey scale or B-mode look-uptable 314, such as being separate portions of a same memory or beingseparate memories. The graphics overlay data, C-mode data, and B-modedata may use independent color schemes. The color schemes may havedifferent formats, such as number of bits.

Using any desired mapping function, each C-mode ultrasound data value isconverted to a display value, such as RGB components. The mappingfunction is linear or non-linear. The mapping function may distinguishbetween directions, such as providing a shade of red for towards thearray and a shade of blue for away from the array. Alternatively, themapping function does not distinguish between directions, such as formapping power information. Brighter colors may be used for larger orsmaller C-mode values.

The processor 112 selects the B-mode display values, C-mode displayvalues, or graphics overlay values for a given pixel in each image. Themultiplexer 310 performs the selection based on output from thecomparator 300. Alternatively, the selection is performed prior tocoordinate scan conversion and/or prior to conversion to display values.

The assignment or allocation of a display value to a pixel is a functionof prioritization of image information. For example, during each frameor multiple frames, each pixel is assigned video information. Dependingon the screen dimensions of the display 116 or customization of imagequality or dimensions, the processor 112, for example, assigns aCartesian coordinate or other location information to each pixel. Then,based on the type of image to be generated as well as the selection ofany region of interest, the appropriate text, border, tissue, and/ormotion or flow RGB value is assigned to the pixel.

To determine which video information has priority, a predetermined chainof priority logic is used. The priority logic is stored on the memory122, and/or multiplexer 310. For example, text information has priorityover all other image data, and border information has the second highestpriority. If a pixel corresponds to text, border, and tissueinformation, the text RGB value is allocated. Alternatively, if a pixelcorresponds to only border and tissue information, the border RGB valueis allocated. In another example, C-mode display values have priorityover B-mode display values in a combined B/C-mode image.

The determination of what graphic overlay information corresponds to arespective pixel is implemented by comparator circuitry. For example,the comparator 300 is operable to determine whether at least one pixelof the plurality of pixels corresponds to a border. The comparator 300receives pixel location values X and Y (304 and 306). The X and Y values304 and 306 are defined as Cartesian coordinates or other locationinformation for a pixel. The comparator 300 also receives the borderdimensions or other graphic overlay location information to determinethe locations of graphic overlay information. For example using aborder, the comparator receive a range width 211, a beam width 215, arange minimum 221, a range maximum 223, a beam minimum 225, and a beammaximum 227 that defines the border. See U.S. Published application Ser.No. ______ (application Ser. No. 11/827,679, filed Jul. 12, 2007), thedisclosure of which is incorporated herein by reference, for one exampleembodiment using the same input reference numbers. The comparator isoperable to compare the X and Y pixel location values 304 and 306 withthe border dimensions to determine if the pixel is in or on a borderarea of the border of a region of interest. Other hardware or logicimplementations than a comparator may be used, such as the processor 120outputting the X and Y coordinates of the graphics overlay data.

The comparator 300 outputs a value 320 as a designation of whether apixel corresponds to the text, border, or other graphics overlay featureor not. For example the value 320 is a flag bit that has a value “0” ifthe pixel being analyzed is not in or on a border area of the border andhas a value “1” if the pixel is in or on the border area of the border.The value 320 is transmitted to the multiplexer 310.

Other flag bits represent whether the different types of information areavailable for a given pixel. Based on the coordinate conversion or otherinformation, flags indicating available data are input to themultiplexer 310. For example, a text validation value 324, a tissuevalidation value 326, and a color validation value 328 are provided. Ifa pixel corresponds to text information, tissue information, or colorinformation, then a “1” is used for the respective values, and a “0” isused if the pixel does not correspond to the respective information.Other flags, such as multi-bit flags, may be used.

The multiplexer 310 uses the validation values 320, 324, 326, 328, and320 in conjunction with the predetermined chain of priority logic.Alternatively, a blending of two or more display values may occur. Forexample, the priority logic may allow both tissue information and borderinformation to be allocated to the same pixel. The display values areaveraged or otherwise combined, such as to allowing tissue to be viewedbeneath a visible but relatively transparent border.

A display value is output for each respective pixel. After themultiplexer 310 receives the display values as well as the validationvalues, the multiplexer 310 outputs the appropriate display value to theappropriate pixel for each pixel in every frame or multiple frames.

The processor 112 outputs the display value for each pixel sequentially.Alternatively, groups of display values are output sequentially, such asassociated with parallel processing. The processor 112 outputs thedisplay values at a pixel rate. The display 116 is clocked to activateeach pixel sequentially. Rather than wait for all display values beforeactivating pixels for a same image, the processor 112 provides thedisplay values as the pixel is to be activated.

FIG. 3 shows one example. The display value for a first pixel (P1) isconverted from ultrasound data. Once the conversion is complete, thedisplay value is output on the display, activating a pixel, at time 1.Then, the display value for the next pixel (P2) is converted fromultrasound data. Once the conversion is complete, the display value isoutput on the display, activating the next pixel, at time 2. The processcontinues sequentially for each pixel on a line of the display, and thenfor the next line of the display to output an image. In otherembodiments, pipeline processing may be used to begin processing thenext conversion (e.g., coordinate conversion ) prior to outputting thepreceding conversion. The completion of conversion and output is stillsequential. One or more pixel or group of pixel buffers may be providedbetween the completion of conversion and output to the display.Alternatively, direct output is provided without buffering.

The processor 112 operates in synchronization with the display 116. Forexample, the horizontal and/or vertical synchronization pulses of thedisplay 116 are also used to time the clock and operation of theprocessor 112. The processor 112 is operated to output the display valuefor each pixel at a time when the display 116 is to receive the displayvalue. The processor 112 operates as a state machine outputting displayvalues and synchronization signals for the display 116.

Referring to FIG. 1, the display 116 receives display values (e.g., RGB)from the processor 112. The display 116 is any mechanical and/orelectronic display. For example, the display 116 is a liquid crystaldisplay (“LCD”), printer, or cathode ray tube (“CRT”) monitor. Analog ordigital displays may be used. The display 116 includes a plurality ofpixels operable to show two dimensional (“2D”), three dimensional(“3D”), and/or four dimensional (“4D”) images (i.e., the fourthdimension is time, and, therefore, 4D images are a sequence of imagesthat show an object over a time period), such as ultrasound images. Eachpixel includes a light source of a given color, such as red, green, andblue light sources. The relative intensity of the light sources at apixel generates a particular color, brightness, hue, and shade for eachgiven pixel.

The display 116 generates an image by sequentially providing pixelvalues by pixel within a line, line-by-line. For a next image, newdisplay values are provided from a first pixel sequentially to a lastpixel. The pixels may be maintained until changed or blanked prior toreceiving the next value.

FIG. 4 is a flowchart of one embodiment of a method of scan conversionin medical diagnostic ultrasound imaging. The method is implemented withthe system 100 of FIG. 1, processor 112 of FIG. 2, or other scanconverter. For example, the method is performed with a handheldultrasound system weighing less than two pounds. The scan conversion isperformed in one housing with a transducer, and display values areoutput to a hinge connected display. Other handheld or non-handheldultrasound imaging systems may implement the method. The method isperformed in the order shown or another order. Additional, different, orfewer acts may be performed. For example, act 404 is provided withoutacts 406 and 408 or vise versa.

Ultrasound data for generation of an image is acquired. For example,C-mode and/or B-mode data is acquired using a transducer. Graphics arealso generated. Any data to be included on a given image is provided.

In act 402, data is converted to display or pixel values for output to adisplay. The data conversion includes coordinate or scan conversion (act404) and/or conversion of value formats (act 406). Other conversions maybe provided.

In act 404, the coordinate conversion is performed. The coordinateconversion alters the ultrasound data based on relative position betweenthe scan format and the display format. For example, a display valueaddress (pixel location) is provided. An acoustic coordinate isdetermined for a display value address. The ultrasound data associatedwith the acoustic coordinate is used to determine a scan convertedultrasound data value at the display value address. A nearest neighborapproach may be used. Alternatively, the scan converted ultrasound datavalue is interpolated from ultrasound data for a plurality of adjacentacoustic coordinates.

The scan conversion is performed for at least one type of data. In oneembodiment, the scan conversion is performed for two or more types ofdata, such as B-mode and C-mode data. A data source is selected for theacoustic coordinate. The data source provides the ultrasound data to bescan converted.

For interpolation, the conversion is performed based on geometricrelationships. The interpolation may be calculated as needed, such asfree of look-up tables for coordinate conversion. Alternatively, look-uptables or other pre-calculation is performed to speed the coordinateconversion.

In act 406, for the display value address, display values are generatedfrom a data source. The ultrasound data is converted to display values,such as RGB values. The scan or coordinate converted ultrasound data isused. For each display value address, display values are provided fromthe ultrasound data. Video display color values are calculated fromacoustic data. For example, look-up tables or other linear or non-linearmapping associates the different possible ultrasound data values todisplay values.

The display values may be determined for B-mode and C-mode imagecomponents. For example, video display color values are calculatedseparately or independently from B-mode acoustic data, C-mode acousticdata, and graphics overlay data. The graphics overlay data may beprovided in the display value format (e.g., RGB). In other embodiments,only one type of data is converted to display values.

In act 408, the display value (e.g., RGB values) for a given pixel isselected. Graphics overlay, B-mode, C-mode, or combinations thereof areselected. For selecting a combination, any combining function may beused, such as averaging or weighted averaging. The selection may bebased on any desired criteria, such as overlay graphics being selectedover other types of data, C-mode having a next priority, and B-modehaving a lowest priority. Where overlay graphics are provided for apixel location, the overlay graphics display value is selected. Whereoverlay graphics are not provided, a C-mode display value is selectedunless not available, then a B-mode display value is selected. Otherpriority schemes may be used.

The display values or ultrasound data may be dithered to increase thedynamic range. Where the conversion of act 406 is independent for thetypes of data, separate dithering may be provided. The B-mode data maybe dithered differently than C-mode data. One B-mode or C-mode data maynot be dithered where the other is dithered. Both B-mode and C-mode datamay be dithered in a same way. The graphics overlay data is notdithered. Dithering for graphics overlay is disabled by not providingthe option to avoid artifacts. In other embodiments, the graphicsoverlay is dithered.

In act 412, the converting of act 402 is synchronized to asynchronization signal of the display. For example, the converting alsogenerates the clocking and/or synchronization signals for driving thedisplay. Pixel timing, line timing, and/or frame timing signals areoutput to the display in correspondence with the generation of thedisplay values to be provided to the display. In alternativeembodiments, the scan converting receives the synchronization signalsfrom the display driver. The display values are generated in timingbased on the received synchronization signals.

The display values are calculated at a rate synchronized with output ofthe video display color values to the display image. Each of the videodisplay color values is calculated as output to a pixel of the displayimage. The conversion is performed as needed for output to the display.For example, each pixel value is scan converted and output prior to scanconverting or completion of scan converting a subsequent pixel value fora same image. The converting is performed at a same rate as theoutputting to the display.

In act 410, the pixel or display values are sequentially output to adisplay. A display image is generated with video display color values.As each pixel or display value is calculated, the value is used tooperate the display at a corresponding pixel location. The pixel ordisplay values are not stored in a memory together with the other valuesto be used to form the same image. Instead, red, green, and blue pixelvalues or other display values are output to the display as created andare created sequentially by pixel or groups of pixels.

Given a sufficiently high pixel rate, a sequence of images is displayedin substantially real time. For example, a frame rate of 30 Hz or betteris provided by activating pixels sequentially.

The imaging system 100 includes instructions that can be executable by aprocessor, such as the processor 120 of FIG. 1, for scan conversion inultrasound imaging. The instructions are stored in a computer-readablemedium, such as the memory 122. The instructions implement the methods,acts, and processes described herein. The instructions for implementingthe processes, methods and/or techniques discussed herein are providedon computer-readable storage media or memories, such as a cache, buffer,RAM, removable media, hard drive or other computer readable storagemedia. Computer readable storage media include various types of volatileand nonvolatile storage media. The functions, acts or tasks illustratedin the figures or described herein are executed in response to one ormore sets of instructions stored in or on computer readable storagemedia. The functions, acts or tasks are independent of the particulartype of instructions set, storage media, processor or processingstrategy and may be performed by software, hardware, integratedcircuits, firmware, micro code and the like, operating alone or incombination. Likewise, processing strategies may includemultiprocessing, multitasking, parallel processing and the like. In oneembodiment, the instructions are stored on a removable media device forreading by local or remote systems. In other embodiments, theinstructions are stored in a remote location for transfer through acomputer network or over telephone lines. In yet other embodiments, theinstructions are stored within a given computer, CPU, GPU or system. Inaddition, any of the features, methods, techniques described may bemixed and matched to create different systems and methodologies.

While the invention has been described above by reference to variousembodiments, it should be understood that many changes and modificationscan be made without departing from the scope of the invention. It istherefore intended that the foregoing detailed description be regardedas illustrative rather than limiting, and that it be understood that itis the following claims, including all equivalents, that are intended todefine the spirit and scope of this invention.

1. A method of scan conversion in medical diagnostic ultrasound imaging,the method comprising: sequentially outputting pixel values to adisplay; and scan converting the pixel values for outputting, each pixelvalue scan converted and output prior to completing scan converting asubsequent pixel value for a same image.
 2. The method of claim 1wherein outputting comprises outputting from the scan conversion withoutstoring the pixel values for the same image together in a memory, theoutputting and scan converting being provided in a handheld ultrasoundsystem weighing less than 2 pounds.
 3. The method of claim 1 whereinscan converting comprises scan converting each pixel value when neededfor output to the display.
 4. The method of claim 1 wherein scanconverting is performed at a same rate as the outputting.
 5. The methodof claim 1 wherein scan converting comprises scan converting free oflook-up tables for coordinate conversion.
 6. The method of claim 1further comprising: synchronizing the scan converting to asynchronization signal of the display.
 7. The method of claim 1 whereinscan converting comprises determining an acoustic coordinate for adisplay value address, determining a data source for the acousticcoordinate, and generating the display values from the data source forthe display value address.
 8. The method of claim 1 wherein outputtingcomprises outputting red, green, and blue pixel values to the display.9. The method of claim 1 wherein scan converting comprises determiningred, green, and blue values from acoustic data for at least B-mode andC-mode image components, and selecting the red, green, and blue valuesfor one of the image components as the display value for a given pixel.10. The method of claim 9 further comprising determining red, green, andblue values for overlay graphics, and selecting the red, green, and bluevalues for the overlay graphics as the display value.
 11. The method ofclaim 9 further comprising: dithering the B-mode image components;independently dithering the C-mode image components; and disablingdithering for overlay graphics components.
 12. A system for scanconversion in medical diagnostic ultrasound imaging, the systemcomprising: a processor operable to convert ultrasound data in anacoustic coordinate format to display values in a Cartesian coordinateformat; and a display operable to receive the display values and todisplay an image with the display values, the image displayed without araster buffer from conversion by the processor to display of the imageby the display.
 13. The system of claim 12 wherein the image isdisplayed without storing display values comprising all pixels of theimage.
 14. The system of claim 12 wherein the processor is operable toconvert the ultrasound data to display values sequentially, the displayvalues comprising red, green, blue values, and wherein the display isoperable to operate a pixel for one display value prior to receiving asubsequent display value for the same image.
 15. The system of claim 12wherein the processor is operable to convert B-mode and C-modeultrasound data, and wherein the processor comprises separate look-uptables for associating the ultrasound values to red, green, and bluecomponents of the display values, the processor operable to select theB-mode or C-mode display values for each pixel in the image.
 16. Thesystem of claim 12 further comprising a transducer connected with theprocessor, wherein the processor, the transducer, and the display arepart of a handheld ultrasound system weighing less than about twopounds.
 17. The system of claim 12 wherein the processor comprises acomparator, the comparator operable to determine if at least one pixelcorresponding to the display is to be based on graphic display values,B-mode display values, C-mode display values, or display values that area combination thereof.
 18. The system of claim 12 wherein the displaycomprises a digital liquid crystal display.
 19. In a computer-readablemedium having stored therein instructions executable by a processor forscan converting in ultrasound imaging, the instructions comprising:generating a display image with video display color values; andcalculating the video display color values from acoustic data, thecalculating being at a rate synchronized with output of the videodisplay color values to the display image, each of the video displaycolor values calculated as the video display color value is output to apixel of the display image.
 20. The instructions of claim 19 whereincalculating comprises calculating the video display color values fromB-mode acoustic data, C-mode acoustic data, and graphics overlay data,and selecting the video display color values for output to the displayimage.